protected void Button1_Click(object sender, EventArgs e)
{
string b = TextBox1.Text;
////截取前两位 123a4a4b5b6 12
//string c = b.Substring(0, 2);
//TextBox1.Text = c;
////截取后两位 123a4a4b5b6 56
//string c = b.Substring(b.Length - 2, 2);
//TextBox1.Text = c;
////截取最后一个字符“a”后面的3位字符 123a4a4b5b6 a4b
//string c = b.Substring(b.LastIndexOf("a"), 3);
//TextBox1.Text = c;
////截取最后一个字符“a”后面所有的字符 123a4a4b5b6 a4b5b6
//string c = b.Substring(b.LastIndexOf("a"));
//TextBox1.Text = c;
////截取最后一个字符“a”前面所有的字符 123a4a4b5b6 123a4
//string c = b.Remove(b.LastIndexOf("a"));
//TextBox1.Text = c;
//// 截取最后一个字符“a”前面所有的字符 123a4a4b5b6 123a4
//string c = b.Substring(0, b.LastIndexOf("a"));
//TextBox1.Text = c;
////截取最后一个字符“a”前面的3位字符 123a4a4b5b6 123a4 3a4
//string c = b.Remove(b.LastIndexOf("a"));
//string d = c.Remove(0, c.Length - 3);
//TextBox1.Text = d;
//// 截取最后一个字符“a”前面的3位字符 123a4a4b5b6 3a4
//string c = b.Substring(2,b.LastIndexOf("a")-2);
//TextBox1.Text = c;
////截取第一个字符"b"前面所有的字符 123a4a4b5b6 123a4a4
//int index = b.IndexOf("b");
//string c = b.Substring(0,index);
//TextBox1.Text = c;
////截取第一个字符"b"前面的3位字符 123a4a4b5b6 4a4
//string c = b.Substring(0, b.IndexOf("b"));
//string d = c.Substring(c.Length - 3, 3);
//TextBox1.Text = d;
////截取第一个字符"b"前面的3位字符 123a4a4b5b6 4a4
//string c = b.Substring(b.IndexOf("b")-3,3);
//TextBox1.Text = c;
////截取第一个字符"b"后面所有的字符 123a4a4b5b6 b5b6
//int index = b.IndexOf("b");
//string c = b.Substring(index,b.Length-index);
//TextBox1.Text = c;
//////截取第一个字符"b"后面3位字符 123a4a4b5b6 b5b
//int index = b.IndexOf("b");
//string c = b.Substring(index, 3);
//TextBox1.Text = c;
////移除从第三位开始的3个字符 123a4a4b5b6 1234b5b6
//string c = b.Remove(3, 3);
//TextBox1.Text = c;
////移除字符串中的所有字符b; 123a4a4b5b6 123a4a456
//string c = b.Replace("b", "");
//TextBox1.Text = c;
////移除字符串中的第一个字符a 123a4a4b5b6 1234a4b5b6
//int index = b.IndexOf("a",1);
//b=b.Remove(index, 1);
//TextBox1.Text = b;
////移除字符串中的第一个字符a的后两位 123a4a4b5b6 123a4b5b6
//int index = b.IndexOf("a", 1);
//b = b.Remove(index, 2);
//TextBox1.Text = b;
////移除字符串中的第二个字符a 123a4a4b5b6 123a4b5b6
//int index = b.IndexOf("a", 2);
//b = b.Remove(index, 2);
//TextBox1.Text = b;
////移除字符串中的第二个字符a的后两位 123a4a4b5b6 123a4b5b6
//int index = b.IndexOf("a", 1);
//b = b.Remove(index, 2);
//TextBox1.Text = b;
////移除字符串中最后一个字符b 123a4a4b5b6 123a4a4b56
//int index = b.LastIndexOf("b");
//string c = b.Remove(b.LastIndexOf("b"),1);
//TextBox1.Text = c;
////移除字符串中最后一个字符b的后两位 123a4a4b5b6 123a4a4b5
//int index = b.LastIndexOf("b");
//string c = b.Remove(b.LastIndexOf("b"), 2);
//TextBox1.Text = c;
////替换字符串中所有的字符“a”,为“b”; 123a4a4b5b6 123b4b4b5b6
//string c = b.Replace("a", "b");
//TextBox1.Text = c;
////替换字符中的第一个字符a为R 123a4a4b5b6 123R4a4b5b6
//int index = b.IndexOf("a");
//string c= b.Remove(index, 1).Insert(index, "R");
//TextBox1.Text = c;
////替换字符中的最后一个字符a为R 123a4a4b5b6 123a4R4b5b6
//int index = b.LastIndexOf("a");
//string c = b.Remove(index, 1).Insert(index, "R");
//TextBox1.Text = c;
////插入I在第一个a之前 123a4a4b5b6 123Ia4a4b5b6
//int index = b.IndexOf("a");
//string c = b.Insert(index, "I");
//TextBox1.Text = c;
////插入I在第一个a之后 123a4a4b5b6 123aI4a4b5b6
//int index = b.IndexOf("a");
//string c = b.Insert(index+1, "I");
//TextBox1.Text = c;
////插入I在最后一个a之前 123a4a4b5b6 123a4Ia4b5b6
//int index = b.LastIndexOf("a");
//string c = b.Insert(index, "I");
//TextBox1.Text = c;
//插入I在最后一个a之后 123a4a4b5b6 123a4aI4b5b6
int index = b.LastIndexOf("a");
string c = b.Insert(index + 1, "I");
TextBox1.Text = c;
}
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